Electrical automatic pilot

ABSTRACT

The invention relates to an automatic pilot for a ruddercontrolled ship of the type in which the motor-operable steering gear for actuating the rudder of the vehicle is controlled by a trigger circuit which in its turn is controlled by an operational circuit including a PID-network. Some ships have a tendency to break out of their course when the rudder is in the midshipposition. It is the object of the invention to provide the pilot with additional means for overcoming this tendency by such a control of the trigger circuit that the rudder is displayed by an angle in excess of that produced by said operational circuit thereby exerting a stabilizing moment on the ship. The additional means comprises an electronic computer having an input receiving the error signal and an output connected to the trigger circuit.

United States Patent [151 3,660,743 Kundler et al. [4 1 May 2, 1972 [54] ELECTRICAL AUTOMATIC PILOT Primary Examiner-Bernard A. Gilheany Assistant Examiner-F. E. Bell 7 z d H t both of l I [77] Inventors gi t g g'figfg ?2 Att0rneyShlesmger, Fitzsimmons & Schlesinger [73] Assignee: Anschutz & Co., G.m.b.H., Kiel-Wik, Ger- [57] ABSTRACT man y The invention relates to an automatic pilot for a rudder-con- Filed: 6, 1970 trolled ship of the type in which the motor-0perable steering [2]] Appl No: 78,497 gear for actuating the rudder of the vehicle is controlledby a trigger circuit which in its turn IS controlled by an operational I circuit including a PlD-network. Some ships have a tendency [52] US. Cl ..318/588, 114/144 [0 break-out f their course when the rudder is i the midship. 1/00 563] 25/02 position. It is the object of the invention to provide the pilot [58] held of Search l 8588* 589; 1 14/144 R with additional means for overcoming this tendency by such a control of the trigger circuit that the rudder is displayed by an [56] References cued angle in excess of that produced by said operational circuit UNITED STATES PATENTS thereby exerting a stabilizing moment on the ship. The additional means comprises an electronic computer having an 5 5/ 1 964 Bentkowsky all input receiving the error signal and an output connected to the 3,5 l 7,2 Kundler trigger ircuit 3,571,684 3/1971 Bech ..318/588 7 4 Claims, 5 Drawing Figures DIRECTION INDICATOR SIGNALLING MEANS COURSE SELECTOR RES|STOR fi':

25 TR|GGER 1 18 RESISTOR. AMPLIFIER U COMPUTER- RUDDER J MOTOR Patented May 2, 1972 2 Sheets-Sheet l ZRESISTOR AMPLIFIER 4 s 8 IIWRESISTOR u RE ISTOR m 3 F,- l I m 5 AMPLIFIER g REs|sToR REsIsTOR 11 9- .2 Fly. 3

[DIRECTION 1 INDICATOR SIGNALLING d MEANS COURSE SELECTOR 19RESISTOR 25 [TRIGGER U 18 RES'STOR AMPLIFIER COMPUTER 1-5 AMPLIFIER ggRESISTOR I. 27 RESISTOR 2s 8 RUDDER a MOT OR INVENT OR BYW'fWL-KQW ATTORNEYS Patented May 2, 1972 3,660,743

2 Sheets-Sheet 2,

' 1 RESISTOR I 4 I 26 [TRIGGER U1 7 18 U- RESISTOR v 22 29 32 Q AMPLIFIER I AMPLIFIER coupursg RUDDER MOTOR TRANSMITTER ZRESISTOR SERVO AMPLIFIER 1 3 34$ERVOMOTOR AMPLIFIER POTENT|OMETER INVENTOR Wat 1! [fund- 1 ATTORNEYS ELECTRICAL AUTOMATIC PILOT Our invention relates to an automatic pilot for a ruddercontrolled ship, more particularly to an automatic pilot of the type in which a direct voltage representative of the course error is applied to a PID-network to a trigger circuit controlling the motor-operable steering gear actuating the rudder of the vehicle.

Some ships, particularly very large ships, display a tendency to break out of their course when the rudder is in the midshipposition and to continue on a circular course. While this tendency has the advantage of making the ship easier to handle by enabling even long ships to turn in a relatively small circle, it has the disadvantage of rendering the exact maintenance of the desired course by an electrical automatic pilot of known design difficult as the pilot is caused by the instability to steer the ship on a sinuous course in which the course angle may oscillate as much as several degrees. These oscillations result in considerable losses in the propelling power of the ship.

It is the object of the invention to equip the automatic pilot with additional means enabling the pilot to overcome thecourse instability and to steer the unstable ship on a straight course. More particularly it is an object of the invention to provide simple, effective and reliable stabilizing means for the pilot which enable the pilot to react to the development of a slight course error by displacing the rudder through an angle in excess of that which would be produced by the pilot in the absence of our novel additional stabilizing means.

The moments of instability trying to swing the ship about its height axis are produced by forces in the vwater. If the ship moves in a dead straight course, the moment of instability is zero. When the angular velocity of the ship moving along a course set by the ships compass increases, the moments of instability increase as well. The direction of these moments is such that the angular velocity of the'ship increases and the ship leaves the set course, without any contribution of the rudder, the direction of change in course depending on minor disturbances which maybe very small and which occur before the ship begins to swing round. The moment of instability which, as stated above, increases at first with increasing angular velocity, diminishes thereafter.

The aforementioned object is achieved in accordance with the present invention by providing in course controlling means of the above described type in addition to the PID-network, an electronic computer whose input end receives the error signal representing the deviation of the ship from the desired course and whose output end is connected directly or indirectly to the trigger circuit switched on for controlling the rudder motor, said electronic computer supplying an output signal by which the rudder is displaced by an angle in excess of that produced by the PlD-network and producing the required compensating moment.

The PlD-network of the course control means causes the rudder of the ship to be set at an angle proportional to the deviation from the course, its differential coefficient and its integral taken over time. The electronic computer which in accordance with the invention is provided in addition to the PID- network causes the rudder to be deflected by an additional angle which is so dimensioned that it causes the rudder to produce a moment about the height axis of the ship in a direction opposite to that of the moment of instability.

The invention will now be described by way of example with reference to the accompanying drawings which show various embodiments thereof.

FIG. 1 is a circuit diagram of an electronic computer provided in accordance with the invention;

FIG. 2 shows a curve, characteristic of the operation of that computer;

FIG. 3 is a circuit diagram of an electronic pilot, the circuit of that pilot switched on for controlling the rudder motor being controlled through a PID-network by a direct'voltage, the Figure showing further the incorporation into the pilot of an electronic computer;

FIG. 4 corresponds to FIG. 3 and shows a modified connection between the electronic computer and the pilot;

FIG. 5 is another embodiment of the electronic computer shown in FIG. 1.

FIG. 3 illustrates diagrammatically by blocks a direction indicator indicating the azimuth of the ship, such as a compass, a course selector adjustable to indicate the desired course of the ship and signalling means connected with the direction indicator and with the course selector for producing an electrical error signal U, which represents the course error of the ship. The automatic pilot functions to so control the motor-operable steering gear 27 as to maintain the ship on the selected course or return the ship thereto in event of any deviation therefrom whereby U will be kept to a minimum.

The invention will be described hereinafter as applied to an electrical automatic pilot of a known type, for instance to a pilot described and claimed in our US. Pat. No. 3,517,285 issued on June 23, 1970. Just as in this prior pilot a signalling means producing the error signal U is connected with a steering gear 27 by electricalconnecting means which include (a) circuit means composed of the elements 17-24 described hereinafter for producing an output voltage causing the steering gear 27 to produce an instantaneous rudder angle composed of three components to be explained hereinafter, (b) a trigger circuit 26 inserted between the circuit means 17-24 and the steering gear 27 and (c) electrical means 28, 25 for producing a feed-back signal connected to the circuit means 17-24. The three components of the rudder angle are a first component proportional to the error signal U,, a second component proportional to the integral of the error signal and a third component proportional to the differential quotient of the error signal.

For the purpose of the present invention there is additionally provided an electronic computer 15 composed of the circuit elements 1-14 shown in FIG. 1 for supplying an output signal to the trigger circuit 26 causing the latter to displace the rudder by an angle in excess of that which would be produced by the connecting means 17-26 in the absence of the computer 15. This additional displacement produces a stabilizing moment on the ship.

The novel electronic computer 15 will now be described with reference to FIG. 1. It comprises the electrical circuit elements 1-14 shown therein.

The voltage U is applied through a capacitor 1 to a computer amplifier 3, bridged by a feed-back resistor 2. In this way an output voltage U: is produced which is approximately proportional to the change of speed of voltage U,. Voltage U produces an auxiliary voltage U;, by means of components 4 to 9 and a computer amplifier 10. The components 4 and 5 are rectifiers and the components 6 to 9 are resistors, all the components being connected to each other as shown in FIG. 1.

The auxiliary voltage U is applied to a potentiometer, consisting of resistors 11 and 12, the potentiometer being so connected to a transistor 13 that the latter becomes conductive when the voltage U exceeds a predetermined value. The transistor 13 is connected through a resistor 14 to the output side of the computer amplifier 3, an output voltage I), being taken from a tapping point between transistor 13 and resistor 14. An increase in the speed of change of the voltage U I causes at first the output voltage U, to increase as well. When the speed of change of the voltage U exceeds a certain value, the voltage U decreases. The relationship between the change of speed of the voltage U and the voltage U is shown by the curve of FIG. 2.

From the above it will appear that the electronic computer 15 comprises a first amplifier network 1, 2, 3 for supplying the output voltage U a second amplifier network 4-12 for supplying the auxiliary output voltage U,, and the transistorized network l3, 14 having an output for supplying the voltage U to the trigger circuit 26 either indirectly through the circuit means 17-24 as shown in FIG. 3 or directly, as described later.

As stated hereinabove, the connection of the signalling means with the motor-operable steering gear 27 shown in FIG. 3 comprises (a) circuit means 17-24, (b) the trigger circuit 26 and (c) electrically means 28, 25 for producing a feed-back signal to the circuit means. These circuits a, b and c will now be described with reference to FIG. 3. The circuit means (a) consists of a computer amplifier 22 whose input end is connected to a resistor 18 and to a capacitor 17, parallel thereto. A feed-back resistor 19 being further arranged in parallel to the amplifier 22 and the input end of the amplifier being connected to a capacitor 21 and a resistor 20 which are both in series. Arranged in advance of the components 20 and 21 is a further computer amplifier 24 which is bridged by a feed-back resistor 23 and at whose input end there is arranged a resistor 25. The output of the computer amplifier 22 controls the trigger circuit 26 which in turn controls the motor-operable steering gear 27 whereby the rudder is set. A detailed description of the trigger circuit 26 is deemed dispensable herewith as it may be similar to that shown and described in our prior U.S. Pat. No. 3,517,285.

The electrical means for producing the feed-back signal comprises a potentiometer 28 the wiper of which is connected with the rudder motor for displacement in proportion to the rudder angle. The voltage taken from the potentiometer serves as a feed-back signal of the rudder angle and is applied to the resistor 25. The voltage U, which indicates the deviation of the ship's course is applied to the computer amplifier 22, the resistor 18 and the capacitor 17.

As mentioned hereinabove, the trigger circuit 26 controls the rudder motor 27 in such a manner that the angle of the rudder consists of three components:

1. a component P which is proportional to the voltage U,,

2. a component I which is proportional to the integral over time of the voltage U,,

3. a component D which is proportional to the differential coefficient of the voltage U,.

The electronic computer shown in FIG. 1 is attached to the above-described electronic pilot for the purpose of compensating moments of instability in the ships course. The computer 15 is connected by a switch 29 to the input side of the course controller and can be disconnected at any time by opening that switch. In the latter case the pilot operates as a normal PlD course controller. When the switch is closed, the output end of the electronic computer 15 supplies the voltage U, to the computer amplifier 24 through a resistor 16. This has the effect that in the case of very small speeds of change in the deviation from the ships course the rudder is deflected by an additional angle, proportional to the voltage U The coefficient of proportionality can be adjusted by adjusting the resistor l6 and thereby adapted to the moment of instability. In the case of some ships, moments of instability do not occur, when the ship carries a certain load. The switch 29 can then be opened.

There exist several possibilities for incorporating the electronic computer 15 into the PID pilot. FIG. 4 shows another one of them. According to this FIG., the output end of the electronic computer 15 is connected to the summing point of the computer amplifier 22 through the adjustable resistor 16, a computer amplifier 30 and a resistor 32. The computer amplifier 30 is bridged by a feed-back resistor 31. A feed-back signal from potentiometer 28 and corresponding to the rudder angle is applied to the summing point of the computer amplifier 22 through a capacitor 21 having a capacity C and an adjustable resistor having a resistance R. If the time constant RXC is very large, the additional rudder angle is practically proportional to the voltage U,,.

The two circuits shown in FIGS. 4 and 5 have in common that the output signal of the electronic computer 15 is applied at a point in advance of the computer amplifier 22. It is also possible to apply the output signal with the aid of a computer amplifier to a point between the computer amplifier 22 and the trigger 26.

FIG. 5 shows a modified electronic computer which is incorporated into the PID circuits. The electronic computer shown in this FIG. is identical with that shown in FIG. 1 as regards components 1-3. In contrast to the computer of FIG. 1 the voltage U which is proportional to the change of speed of the deviation fromthe course is a plied in the case of FIG. 5 to a servo amplifier 33 which con rols a servo motor 34. The

servo motor adjusts a potentiometer 35 whose output voltage is fed back to the input side of the amplifier 33. The servo motor also adjusts a transmitter 36 whose output voltage represents the voltage U and corresponds to the curve of FIG. 2. The transmitter 36 may be a non-linear potentiometer with corresponding taps, whilst the potentiometer 35 has a linear characteristic.

It is obvious that numerous changes may be made in the form and construction of the invention without departing from the material spirit thereof. Therefore, the invention is not limited to the exact form shown and described with reference to the drawings but includes all modifications as properly come within the scope claimed.

What we claim is:

1. An electrical automatic pilot for a rudder-controlled ship comprising a direction indicator, an adjustable course-selector, signalling means connected with said direction indicator and with said course-selector for producing an electrical error signal representing the course error of the ship, an electrically controlled motor-operable steering gear for actuating the rudder of the vehicle, electrical connecting means connecting said signalling means with said steering gear, said connecting means having an input connected to said signalling means and an output cooperatively connected to said steering gear, said connecting means including (a) circuit means for producing an output signal causing said steering gear to produce an instantaneous rudder angle composed of three components, the first one of said components being proportional to said error signal, the second component being proportional to the integral of said error signal and the third component being proportional to the differential quotient of said error signal, (b) a trigger circuit inserted between said circuit means and said steering gear and (c) electrical means for producing a feedback signal connected to said circuit means, and an electronic computer for producing an output signal by which the rudder is displaced by an angle in excess of that produced by said connecting means, said electronic computer having an input connected to said signalling means to receive said error signal therefrom and an output connected to said trigger circuit, whereby a stabilizing moment is exerted on the ship.

2. An electrical automatic pilot as claimed in claim 1 in which said electronic computer comprises a first amplifier network for supplying an output voltage corresponding in magnitude and sign to the differential quotient of said error signal, a second amplifier network for supplying an auxiliary output voltage corresponding in magnitude to that of said differential quotient, and a transistorized network havingan input connected to the outputs of said first amplifier network and said second amplifier network, the output of said transistorized network being the output of said electronic computer, the input of said electronic computer being connected to the inputs of said amplifier networks.

3. An electrical automatic pilot as claimed in claim 2 further comprising an adjustable resistor included in the connection between the output of said electronic computer and said trigger circuit for varying the magnitude of said excess.

4. An electrical automatic pilot as claimed in claim 1 further comprising a manually operable switch for disabling said electronic computer. 

1. An electrical automatic pilot for a rudder-controlled ship comprising a direction indicator, an adjustable course-selector, signalling means connected with said direction indicator and with said course-selector for producing an electrical error signal representing the course error of the ship, an electrically controlled motor-operable steering gear for actuating the rudder of the vehicle, electrical connecting means connecting said signalling means with said steering gear, said connecting means having an input connected to said signalling means and an output cooperatively connected to said steering gear, said connecting means including (a) circuit means for producing an output signal causing said Steering gear to produce an instantaneous rudder angle composed of three components, the first one of said components being proportional to said error signal, the second component being proportional to the integral of said error signal and the third component being proportional to the differential quotient of said error signal, (b) a trigger circuit inserted between said circuit means and said steering gear and (c) electrical means for producing a feed-back signal connected to said circuit means, and an electronic computer for producing an output signal by which the rudder is displaced by an angle in excess of that produced by said connecting means, said electronic computer having an input connected to said signalling means to receive said error signal therefrom and an output connected to said trigger circuit, whereby a stabilizing moment is exerted on the ship.
 2. An electrical automatic pilot as claimed in claim 1 in which said electronic computer comprises a first amplifier network for supplying an output voltage corresponding in magnitude and sign to the differential quotient of said error signal, a second amplifier network for supplying an auxiliary output voltage corresponding in magnitude to that of said differential quotient, and a transistorized network having an input connected to the outputs of said first amplifier network and said second amplifier network, the output of said transistorized network being the output of said electronic computer, the input of said electronic computer being connected to the inputs of said amplifier networks.
 3. An electrical automatic pilot as claimed in claim 2 further comprising an adjustable resistor included in the connection between the output of said electronic computer and said trigger circuit for varying the magnitude of said excess.
 4. An electrical automatic pilot as claimed in claim 1 further comprising a manually operable switch for disabling said electronic computer. 